Threaded fine adjustment means used in building and concrete construction equipment are often damaged by dirt and mud in threads, rough handling and necessity to smash hardened concrete off threads. In the case of the latter, if the basic adjustment means were essentially flat it could be placed on a concrete slab or suitable piece of steel and cleaned with concrete-breaking equipment. An object of the basic invention is the provision of a passive, heavy-duty, essentially flat adjustment mechanism, more or less capable of being cleaned as described, or, when necessary, of being field-renovated with a hammer, without appreciable loss of function. Other and further objects of this invention, not the least of which is preservation of timber, will be pointed out hereinafter or will be indicated in the appended claims or will be obvious to one skilled in the art upon an understanding of the present disclosure.